Reflection on immediate experience seems to be about as certain as you can get. You may not quite know what is was but that it was and how it was are clear in immediate objectivation. Where some room for doubt remains is in the sense that the certainty does not quite coincide with what it is certain of but belongs to a new moment of reflection, a reflection inflected slightly towards the possibility of things being quite other than they currently are. There is a kind of intuitive architecture of time which tells you where to look for the immediate past. The invariance of this home structure is only contingent, it is given to you, and you habitually take it as given and as it seems to have been for a long time. It is possible to rotate the frame slightly, to stretch it and deform it imaginatively, in other words to practise variations on it, aided by memories if available, or poetic evocations or metaphoric injunctions, of altered states. This the natural way in which subjective ontological structures are tested and if nothing else points to the fact that all such structures are no more than products of imagination. Crystallised imagination is unreflectively taken to be reality, but every such crystallisation can be melted if the temperature of imagination is raised sufficiently. Openings of this kind are never entirely forgotten, and adumbrations of them are valued highly. The verity lies not in any structure but in the banked fires of of what in its downstream form is called imagination.